1. Field of the Invention
This invention relates to an LED lamp system and a method of making the LED lamp system.
2. Description of the Related Art
Conventional LED lamps include a bullet type or SMD (surface mount device). For example, an LED lamp system for a vehicle lamp is constructed such that leads of the LED lamp are soldered to a printed circuit board (PCB) and the PCB is then secured to a case portion, and installed at a given position of the vehicle. The PCB is wired to a lighting control device of the vehicle such that flashing of the LED and brightness or emission color of the lighted LED are controlled by a vehicle switch or a control circuit.
JP-A-2002-036950 and 2001-243829 disclose LED lamp systems that an LED lamp is bonded to PCB. JP-A-2007-184547 discloses an LED lamp system that a circuit portion to which an LED lamp is bonded is formed with a metal board.
The LED lamp system of JP-A-2007-184547 is excellent in heat radiation since the metal board is used instead of the PCB. However, since the metal board is used both as a connection terminal (or connector) for electrical attachment and a circuit portion, external force applied to the connection terminal when attached to, e.g., an external connector on a vehicle may be directly transferred to the circuit. Thereby, electrical or electronic parts etc. mounted on the metal board may cause a malfunction.
In the LED lamp systems of JP-A-2002-036950 and 2001-243829, although the above problem may be solved since connection terminal is soldered to the PCB, the external force when attached thereto is directly applied to a soldering part and a crack or electrical connection failure may be thereby caused to lower the reliability.
In order to solve this problem, the number of the soldering parts may be increased (e.g., as shown in FIG. 4 of JP-A-2002-036950) along the connection terminal for dispersing the external force. However, a certain distance needs to be secured between the soldering part and the circuit portion so as not to transfer heat to the circuit portion during soldering. Thus, when the number of the soldering parts increases, the downsizing of the lamp system will be impaired since a space is further needed to secure the distance and to dispose the soldering parts. Especially in case of an in-vehicle light source, this problem will be more serious since the light source needs to be placed in a very limited space in the vehicle.